Surgeons fix millions of fractures annually using traditional metal alloy or stainless steel implants that become useless and occasionally painful after the fracture has been united. In many cases, in order to prevent the complications and risks associated with the placement and removal of these metal implants, bioresorbable screws and other similar devices have been developed. Such resorbable implants allow for fixation while a slow controlled resorption is underway.
However, where a fracture consists of a metaphyseal or diaphyseal fracture of a long bone such as, for example, the femur, the need has developed for a fracture fixating implant that is significantly larger in dimensions than the typical fixation screw but which is also resorbable to avoid the necessity of secondary surgery to remove fixating components. It is with this thought in mind that the present invention was developed.
The present invention relates to a bioresorbable implant for fracture fixation. The present invention includes the following interrelated objects, aspects and features:
(1) The present invention contemplates the use of a resorbable ceramic material inserted into a special container, the outer dimensions of which may be adjusted during insertion to provide firm fixation. In the preferred embodiment, the ceramic material consists of a material such as Calcium Sulfate (otherwise known as Plaster of Paris) or Hydroxyapatite. Such materials have the characteristic of being mixable in a paste-like form and which begin to set up and harden within several minutes to an hour of their first mixing. Alternative materials that could be employed with equal effectiveness include Collagen Sponge which acts as a scaffolding for the incorporation of bone as proteins are deposited on it, cells invade and it is turned into bone; and Demineralized Bone Matrix or Proteins: the proteins act as a scaffolding in a similar manner as is the case with the Collagen Sponge but it is not organized and it is extracted from existing bone; the protein promotes rapid incorporation and is able to turn the tissue adjacent to the proteins into bone through a process called Osteoinduction.
(2) The special container in which the resorbable ceramic or other material is placed preferably consists of two spaced plugs or plates connected together with a flexible boot and including actuator means allowing adjustment of the spacing between the plugs or plates.
(3) The volume enclosed within the plugs and boot is filled with the resorbable ceramic or other material. As should be understood, as the mechanism moves the plugs toward one another, the material is squeezed and tends to expand radially outwardly, stretching the boot and increasing the outer diameter of the special container. Through this process, the special container can be wedged and fixated in desired position within the location of the fracture.
(4) In the preferred embodiment of the present invention, all of the components of the special container are also bioresorbable so that as the fracture heals, the special container along with the material therein are resorbed within the body as the bone regenerates at the fracture site so that secondary surgery is not required.
(5) In a first embodiment of the special container, the actuator means consists of a spring biasing the two plugs together and a plunger that may be manipulated by the surgeon to separate the plugs to make the outer dimensions of the special container as thin as possible when it is being placed at the fracture site. When pressure is released on the plunger, the spring biasing force moves the plugs toward one another to expand the material outwardly against the flexible boot to wedge and fixate the special container in place.
(6) In a second embodiment of the present invention, a central shaft or rod is threaded through both of the plates. One plate has right-hand threads in an opening therethrough and the other plate has left-hand threads in an opening therethrough. The rod has threads complementary to each of the right-hand and left-hand threads in the respective plates, such that rotation of the rod in one direction causes the plates to move toward one another and rotation of the rod in the opposite direction causes the plates to move away from one another. Thus, with the material inserted within the special container, the rod is rotated to separate the plates from one another as far as possible so that the special container adopts the thinnest possible profile. After the special container is inserted within the fracture site, the rod is rotated in the opposite direction to move the plates toward one another and cause the material to spread outwardly expanding the flexible boot and wedging the special container at the fracture site.
Accordingly, it is a first object of the present invention to provide a bioresorbable implant for fracture fixation.
It is a further object of the present invention to provide such a device in which a resorbable ceramic material is contained within a resorbable special container having an actuator means allowing it to be placed at a fracture site and wedged in place to provide fracture fixation.
It is a further object of the present invention to provide such a device in which a Collagen Sponge material is contained within the resorbable special container.
It is a still further object of the present invention to provide such a device in which Demineralized Bone Matrix or Proteins are contained within the special container.
It is a still further object of the present invention to provide such a device in which two spaced plugs are connected by a flexible boot to define an internal chamber containing the resorbable ceramic material.
It is a yet further object of the present invention to provide an embodiment in which a spring provides a biasing force tending to move the plates toward one another.
It is a yet further object of the present invention to provide such a device in which right-hand and left-hand threads are used in an actuator mechanism designed to move the plates toward and away from one another.
These and other objects, aspects and features of the present invention will be better understood from the following detailed description of the preferred embodiments when read in conjunction with the appended drawing figures.